The present invention relates to flexible tube systems for use in automotive exhaust systems, and particularly to flexible exhaust tubes having shielded and insulated portions for improved performance.
In the automotive industry, particularly the segments for on-road and off-road trucks, agricultural equipment and heavy equipment, exhaust systems can require a flexible tube portion to connect misaligned components and to decouple the components from each other and thereby reduce the effects of vibrations and relative movements of the components. Various flexible tubes are used to accomplish this task, including decouplers and spiral wound gas-tight hoses. Such tubes and hoses (referred to herein collectively as “tubes”) typically have exposed recesses and cavities into which dust, dirt, and agricultural chaff can accumulate.
Flexible exhaust tubes of the type described herein, are assemblies of a number of different parts and subassemblies. Given the complexities of each of the component parts and their respective manufacturing techniques, the parts are typically manufactured by separate companies and assembled before sale and installation.
For example, the flexible central portion can be a bellows or a gas-tight hose requiring specialized manufacturing facilities and techniques. The tube end portions joined to each end of the flexible central portion typically are rigid with bends and elbows, and therefore are manufactured by a separate company with related expertise. The rigid tube end portions are then wrapped in insulation and an outer thin foil before being attached to the central flexible portion. The insulated tube subassemblies must be robust so they can be shipped, handled, and assembled without damage. One way to protect the insulation, for example, is to add a termination ring that is mounted on each rigid end portion and spaced apart from the end of the end tube portion nearest the central flexible portion. The termination ring provides an attachment location for the outer thin foil sheet used to protect the insulation, and is spaced apart from the end of the end tube portion to provide adequate clearance for handling and assembly to the central flexible portion. Once these end tube portions are joined to each end of the central flexible portion, the assembly is shipped to another party for installation in an exhaust system.
This type of assembly results in a robust flexible exhaust tube that decouples unaligned upstream and downstream components such as an upstream engine and a downstream catalytic converter, from vibrations and variable movements as a vehicle travels on road or off. While satisfactory, the described assembly has shortcomings because the termination rings leave exposed and uninsulated tube portions that can result in cooling of the hot exhaust gases passing through the assembly. Further, the exposed tubes become quite hot during use and expose operators and repair personnel to possible injury. The exposed tube portions also define crevices where dirt, debris, and chaff from agricultural operations can accumulate and possibly ignite from the high tube temperatures.
Thus, there is a need for improved flexible tubes for use in automotive exhaust systems.